Surface ornamentation for riding lawnmower



FIG. 1 is a right side view of the surface ornamentation for riding lawnmower, showing my new design, the broken line showing of the mower is for illustrative pusposes only, and forms no part of the claimed design;

FIG. 2 is a left side view thereof;

FIG. 3 is a rear view thereof; and,

FIG. 4 is a top view thereof. 

The ornamental design for a surface ornamentation for riding lawnmower, as shown. 